Wine Country Wildfires: Reconnaissance and Loss Estimate Update

Figure 1: A door frame of a destroyed home overlooks another neighborhood affected by the Wine Country wildfires (Image credit: RMS)

Accompanied by a CAL FIRE escort, on Monday, October 23, RMS reconnaissance experts visited areas affected by the Wine Country wildfires, with a focus primarily on the Tubbs Fire which caused destruction across the Northern California counties of Napa, Sonoma, and Lake. Based on this reconnaissance, RMS has now updated its loss estimate, benefiting from an additional review of the available damage information, plus a review of historical fire damage data.

Figure 2: Map showing the perimeter of the Tubbs Fire (CAL FIRE) and the reconnaissance track taken by RMS.

RMS estimates an economic loss for the wildfires impacting Sonoma, Napa, Solano, Lake, and Mendocino counties between US$6 billion and US$8 billion. This range includes loss due to property damage, contents and business interruption caused by the fires to residential, commercial, and industrial lines of business. Automobile or agricultural crop losses are not included. High penetration rates of wildfire coverage in standard homeowners and commercial policies implies similar insured losses.

As a comparison, for the 2015 Valley Fire in Lake County, CA, Property Claims Services reported roughly US$1 billion in insured losses. This estimate was based on 1,900 destroyed structures. CAL FIRE currently estimates four times as many structures (7,800 destroyed and 600 damaged structures), with higher average insured values compared to the Valley Fire.

High-resolution fire perimeters are now available from the Geospatial Multi-Agency Coordination (GeoMAC) to define the exposed commercial and residential exposure boundary of the Wine Country fires. Using this GeoMAC data, the RMS high-resolution exposure database identifies approximately 11,000 structures and more than US$10 billion in total exposure lie within the fire footprints. Please note that this is a reduction from prior estimates derived from lower resolution perimeters.

With reports of 8,400 damaged or destroyed structures, this indicates that the proportion of properties affected equates to roughly 70 to 75 percent, which is the highest proportion observed in the RMS review of historical events of this scale and magnitude. Looking at the figure below, this research has shown typical percentages of affected structures ranging between 15 to 50 percent. Lower percentages in the Cedar and Witch fires are believed to be due to the type of vegetation, lower canopy density, and heightened awareness of wildfire risk in the San Diego area.

Figure 4: Percentage of damaged or destroyed structures within a fire footprint.

RMS reconnaissance confirms the high percentage of affected structures within the footprints. Multiple neighborhoods, even outside the well-documented damage in the Coffey Park neighborhood in Santa Rosa, experienced widespread destruction beyond ranges seen in historical events. This includes residential structures ranging from mobile homes to multi-family apartment complexes and high-value single family dwellings.

Figure 5: A hilltop view of wildfire damage near Fountaingrove Parkway, just north of Santa Rosa (Image credit: RMS)

Impact of Embers

Figure 6: Typical large ember found near a home burned in the Tubbs Fire (Image credit: RMS)

Reconnaissance also highlighted the impact of embers and the large ember accumulations observed around exposures in areas farther away from significant burnable fuels (e.g. trees and large bushes). The effects of embers greatly increased the risk at these locations — including the Coffey Park neighborhood, which experienced nearly 100 percent destruction. Ember risk, driven by the extreme Diablo winds observed during the initial hours of the fires, is likely the primary driver of the increased damage seen within the perimeters and urban areas downwind of significant burnable fuel.

Sources of uncertainty remain with this event loss estimate, including the impacts of demand surge and business interruption costs to the wine industry. These unknown factors, in addition to costs associated with debris removal and building code compliance for new construction, may result in further increases to the total loss from this event.

Senior Product Manager, Model Product Management
As a senior product manager in the Model Product Management group at RMS, Kevin is responsible for RMS climate-peril products for the Americas, including wildfire and custom vulnerability analytics. Kevin has been actively involved in model releases for both severe convective storm and hurricane models over the last four years at RMS. Kevin holds a master’s degree in atmospheric science from the University of Illinois at Urbana-Champaign, where he authored a thesis on tornado-genesis and severe convective storms, and a bachelor’s degree in atmospheric science from Purdue University. He also holds the Certified Catastrophe Risk Analyst (CCRA) designation from RMS. Kevin is a member of the American Meteorological Society (AMS), a mentor for the AMS Board of Private Sector Meteorologists, and a voting member of the ASCE Standards Committee on Wind Speed Estimation in Tornadoes.